graphics: CONTOUR-PARAMETERS
The maximum number of bisections that is allowed to find a coarse
starting point for a new contour between 2 grid points.
Small values are recommended since a Newton search anyhow refines
the starting point.
[Default: 10]
The epsilon used to compute the gradient.
For coordinates near 0, this is the absolute sampling size. For
large coordinates, the parameter is taken relative.
When the area is very small (e.g. around 10**-3) or when there
is a lot of structure in the contours, then it is a good idea to
reduce the value of this parameter to e.g. 10**-4.
[Default: 10**-3]
The epsilon used to follow a contour perpendicularly to the
gradient.
For coordinates near 0, this is the absolute step size. For
large coordinates, the parameter is taken relative.
When the area is very small (e.g. around 10**-3) or when the
contours make sharp bends, then it is a good idea to reduce
the value of this parameter to e.g. 10**-4.
[Default: 10**-3]
Since the contours are piecewise straight, it can be that a
contour segment does not appear to pass between 2 grid points
between the exact contour would pass.
In such cases, the algorithm checks whether the contour passes
near a grid point within a certain fraction of the grid size,
set with this option.
This parameter rarely needs updating. If the parameter is too
small, then some contours will be drawn twice. Contours are not
missed due to a poor setting of this parameter.
[Default: 0.1]
Maximum number of Newton iterations when refining the starting
point of a contour and when finding the contour back after a
step perpendicular to the gradient.
[Default: 10]
Maximum number of steps in any single contour.
If this parameter is too small, then the contours will be drawn
as a series of overlapping pieces.
[Default: 500]
Keyword index.
Formatted on 10/11/98.